Quenching oil and method for quenching metals



Patented Oct. 18,' 1949 QUENCHING' OIL AND METHOD FOR QUENCHING METALS Gerard S. Manes, West Englewood, N. J., and Louis H. Sudholz, Flushing, N. Y., assignors to Socony-Vacuum Oil Company, Incorporated, a

corporation of New York No Drawing. Application February 22, 1945, Serial No. 579,316

11 Claims. (Cl. 148-131) This invention relates to oils to be used for quenching highly heated metals especially ferrous alloys such as carbon and alloy steels. It specifically relates to a new and improved quenching oil and the use thereof.

Many metal alloys, particularly ferrous alloys and carbon steels require heat treatment for development of increased hardness and strength. The hardness and strength of a given alloy is dependent largely upon certain physical structure. In the case of steel, the hardenability is determined by the proportion of martensite obtainable mineral oil. However, the use of aqueous quenching baths results in setting up excessive internal stresses in the metal alloy, causing distortion, warping and, in some cases, cracking. Mineral oils as quenching baths have the valuable property of cooling the steel slowly after it has been reduced to about 600 F. to 700 F. It has the added advantage of maintaining a substantially uniform quenching speed over a wide range in temperature variation of the quenchin bath itself. These valuable properties tend to minimize internal stresses and distortion in the metal alloy.

The disadvantage of ordinary mineral oils as quenching media is that they do not offer the desirable high initial quenching rates that are characteristic of aqueous baths. This disadvantage is particularly important in the manufacture of certain steels having high critical cooling rates. Ordinary mineral oils when used as quenching baths for such steels do not ofier initial quenching speeds sufficiently high to effect maximum steel hardness. From the above, it will be apparent that the development of quenching media offering initial quenching or cooling speeds approachin that of water and retaining the hereinabove mentioned valuable characteristics of mineral oil 2 media is a development of considerable importance.

It is the major object of this invention to provide an oil-type metal quenching fluid exhibiting very high initial quenching speeds.

Another object of this invention is the provision of a new and improved method for quick-quenching or hardening alloy metals. These and other objects of this invention will become apparent from the following description.

This invention is based on the discovery that alkyl-substituted polynuclear aromatic hydrocarbons have all the advantages of ordinary mineral oils as quenching media and exhibit initial quenching speeds far surpassing those of ordinary mineral oils. It has also been discovered that small admixtures of such aromatic hydrocarbons with a conventional mineral oil raise the initial quenching speed of the latter much more than would be expected from the proportion of the two components in the blend.

Before proceeding with the description of this invention, certain terms used in describing and in claiming this invention will now be defined. The terms ordinary mineral oil or conventional mineral oil are intended to mean mineral oils derived from petroleum which are substantially free of alkyl-substituted polynuclear aromatic hydrocarbons, said mineral oils boiling above about 550 F., having a flash point by the Cleveland open cup method above about 300 F. and a viscosity over about seconds and below about 200 seconds upon the Saybolt viscosimeter. The term alkyl-substituted is intended to cover either a substituted saturated or unsaturated aliphatic group or both.

Those aromatics which have been found particularly valuable as metal quenching media are alkyl-substituted naphthalenes, anthracenes and phenanthrenes. Such aromatic oils may be prepared by the multipass catalytic conversion of gas oil or fuel oil cracking stocks. For example, when a Mid-Continent gas oil, boiling within the range about 450 F. to 900 F. is subjected in the vapor phase to a solid adsorptive catalytic material such as Super Filtrol rclay, synthetic silica and. alumina-containing gel catalysts, or certain natural clays at a pressure usually above atmospheric and at temperatures of the order of 800 F. and upwards, gasoline, gas, cycle stock and a small 3 amount of cokey material are obtained as products. The cycle stock is then again subjected to a similar catalytic conversion step and the cycle stock resulting from the latter step may be or may not be again subjected to catalytic conversion.

Ultimately the cycle stock which remains after two or more catalytic conversion steps is fractionated to provide a hydrocarbon cut having the following broad properties:

Gravity--A. P. I 8 maximum Flash point, Cleveland open cup 300 F. minimum Saybolt Universal viscosity at 100 F 60 seconds minimum This out has been found to consist principally of a mixture of alkyl-substituted di-nuclear and tri-nuclear aromatic hydrocarbons. Such a hydrocarbon cut when used as a quenching fluidhas been found to be far superior to ordinary mineral oils as hereinabove pointed out. A similar cut may be obtained from a cycle stock from a catalytic recycle hydrocarbon process. Similar hydrocarbon cuts may also be obtained from other sources such as coal tar and are intended to be included within the scope of this invention provided they conform with the broad properties set forth hereinabove. In addition to the above properties, it may be generally stated that the alkylsubstituted polynuclear aromatic hydrocarbons used as quenching fluid should boil within the broad'range of temperatures 550 F. to 800 F, and have a Saybolt Universal viscosity within the range 60 to 200 seconds at 100 F.

Exemplary of a preferred quenching fluid according to this invention is a cut prepared from a cycle stock from a multipass catalytic conversion process which has approximately the following properties:

The above preferred oil will be hereinafter referred to as aromatic oil A for purposes of discussion.

It is quite common in the industry to compare quenching media by reference to their initial quenching speed as measured by the initial second quench test. The initial 5 second quench rating is determined according to the following formula:

Temperature rise in 5 second test Temperature rise in cold quench test Per cent available heat removed in first 5 seconds The values used in the above calculation are determined as follows:

A stainless steel sphere of definite weight (200 grams) is heated in an electric furnace, equipped with automatic control for minutes at 1500 F. A definite quantity of the oil to be 4 tested is placed in a calorimeter equipped with an agitator which revolves at a definite speed.

The heated test piece is immersed in the quenching bath which was initially at 90 F. for 5 seconds and the maximum bath temperature reached is observed. A second test piece is immersed in the quenching bath, initially at 90 F. and the bath agitated until a maximum rise in bath temperature has been effected. By substituting the values obtained in the above formula for the 5 second quench and for thecoldquench, the 5 second quenching speed can be determined.

The following table gives the comparison of initial quenching rates determined in the above manner between the preferred hydrocarbon out having the properties above set forth and two conventional mineral oil cuts having approximately the same boiling range, flash point and viscosity.

5Initiald secon Quenching Media Quenching Speed 7 Per CtII/t Conventional paraffin base mineral oil 21.0 Conventional Mid-Continent base mineral oil containing some paraflins 14.3 Preferred Aromatic Oil A I 3930 5Initiald secon Blend Quenching Speed.

Per cent Conventional Mid-Continent base mineral oil containing some para 14:3 Conventional Mid-Continent base mineral oil contaming some paraffins+l.0% Aromatic Oil A 123;) Conventional Mid-Continent base mineraloil con-- taining some parafiins+2.5% Aromatic Oil A 21.8 Conventional Mid-Continent base mineral oil containing some parafiins+5.0% Aromatic 011 A 20.6 Conventional Mid-Continent base mineral oil containing some parafiins+10% Aromatic Oil A 21: 7 Conventional Mid-Continent base mineral oil contaming some paraifins+25% Aromatic Oil .A. 21.7 Conventional Mid-Continent base mineral oil 'containing some parafiins+% Aromatic'Oil "A 27. 6

It will be noted that theaddition of the first few percentages of aromatic oil-A promoted the quenching speed of the Mid-Continent oil; far in excess of what would be expectedfor the .small proportion of aromatic oil A added. Thus, for addition of 1.0% aromaticoil A, the quenching speed on a strictly proportional blending basis would be about 14.5%, whereas it'was'in fact 23.0%. In other words, theblend'ing' value of the first 1% of aromatic oil A. is about-i0 to 50 times as great as would be'expected onla strictly proportional blending basis. The optimum percentage of alkyl-substituted polyrmclear aromatic hydrocarbons that shouldbe addeddzo a given conventional mineral. oil will depend largely on the characteristics of the mineral oil involved but may be stated broadly as'between about 0.5% to 5.0% by volume of the mineral oil. The mineral oil used in such blends should in general boil within the range 550 F. to 800 F., have a flash point above about 300 F. and have a viscosity within the range 60 to 200 seconds at 100 F. (S. U. V.). It should be understood, however, that this invention broadly covers alkylsubstituted polynuclear aromatic hydrocarbons boiling above 550 F. as a metal quenching fluid either in the substantially pure form or in any practical admixture with conventional mineral oils, and the method of quick quenching metal alloys by immersion thereof in baths comprised of such fluids. It should be further understood that this invention is not to be construed as limited to any specific examples of the quenching fluid given hereinabove nor to any of the exemplary methods for its preparation or use except as limited by the following claims.

We claim: I

1. An improved method for quenching heated metals which comprises quickly immersing said heated metal in a fluid bath consisting principally of alkyl-substituted polynuclear aromatic hydrocarbons boiling within the range 550 Fahrenheit to 800 Fahrenheit.

2. A method for hardening metals which comprises heating said metal to a red heat and quickly immersing it into a relatively low temperature bath consisting principally of a mixture of alkylsubstituted di-nuclear and alkyl-substituted trinuclear aromatic hydrocarbons boiling above about 550 Fahrenheit and having a viscosity above about 60 seconds at 100 Fahrenheit.

3. A method for quick-quenching heated metals comprising quickly immersing said heated metal into a bath consisting of a mixture of a conventional mineral oil boiling within the range about 550 Fahrenheit to 800 Fahrenheit and from 0.5 to 5.0% by volume of alkyl-substituted polynuclear aromatic hydrocarbons boiling within the range about 550 Fahrenheit to 800 Fahrenheit.

4. A method for hardening metals which comprises heating the metal to a red heat and suddenly immersing said heated metal into a bath consisting of a mixture of conventional mineral oil, and alkyl-substituted di-nuclear and alkylsubstituted tri-nuclear aromatic hydrocarbons,

said mixture boiling within the range 550 Fahrenheit to 800 Fahrenheit and having a viscosity within the range 60 to 200 seconds at 100 Fahrenheit, said mixture containing an amount of said alkyl-substituted di-nuclear and alkyl-substituted tri-nuclear hydrocarbons suflicient to insure an initial quenching speed of said mixture substantially greater than that of said conventional mineral oil alone.

5. A method for quenching heated metals which comprises quickly immersing the heated metal in a mineral oil bath containing at least 0.5 per cent by volume of alkyl-substituted polynuclear aromatic hydrocarbons boiling above about 550 F. and having a viscosity above about 60 seconds at 100 Fahrenheit.

6. A method for quenching heated metals which comprises quickly immersing the heated metal in a bath consisting substantially of a mixture of normally liquid alkyl-substituted di-nuclear and alkyl-substituted tri-nuclear aromatic hydrocarbons, said mixture boiling within the range 575 Fahrenheit to 750 Fahrenheit, having a flash point above about 330 Fahrenheit, having a viscosity within the range 100 to 150 6 tive index at 20 C. within the range 1.60 to 1.64.

7. A method for quenching heated metals which comprises quickly immersing the heated metal in a mineral oil fluid bath containing at least 0.5 per cent by volume of alkyl-substituted naphthalenes, boiling within the approximate range 550 Fahrenheit to 800 Fahrenheit.

8. A method for quenching heated metals which comprises quickly immersing the heated metal in a hydrocarbon oil fluid bath containing at least 0.5 per cent by volume of alkyl-substituted anthracenes, boiling within the approximate range 550 Fahrenheit to 800 Fahrenheit.

9. A method for quenching heated metals which comprises quickly immersing the heated metal in a mineral oil fluid bath containing alkyl-substituted phenanthrenes, boiling within the approximate range 550 Fahrenheit to 800 Fahrenheit.

10. A method for hardening metals which comprises heating the metal to a red heat and quickly immersing said heated metal in a fluid bath consisting principally of a mixture of alkyl-substituted naphthalenes, alkyl-substituted anthracenes, and alkyl-substituted phenanthrenes boiling in the approximate range 550 Fahrenheit to 800 Fahrenheit.

11. The process for quenching heated metals which comprises quickly immersing the heated metal in a bath consisting of a hydrocarbon cut composed principally of alkyl-substituted polynuclear aromatic hydrocarbons and boiling within the range about 550 F. to 800 F. and having a refractive index above about 1.59 at 69 F. prepared by subjecting a petroleum fraction boiling above the boiling range of gasoline to a controlled catalytic cracking operation in the presence of a particle form adsorbent material, fractionating a cycle stock boiling above gasoline from the gaseous products from said cracking operation and subjecting said cycle stock to at least one additional controlled catalytic cracking operation, and fractionating the gaseous products from the last catalytic cracking operation to provide said hydrocarbon cut.

GERARD S. MAPES. LOUIS H. SUDHOLZ.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PA'I'ENTS Number Name Date 57,349 Manning Aug. 8, 1866 1,535,379 Rodman Apr. 28, 1925 1,666,426 Ruths Apr. 17, 1928 1,818,431 Rodman Aug. 11, 1931 1,878,509 Michel Sept. 20, 1932 2,006,202 Huyser June 25, 1935 2,031,431 Shepherd Feb. 18, 1936 2,033,702 Grebe et a1 Mar. 10, 1936 2,340,724 Horst et a1. Feb. 1, 1944 2,416,479 Helmars Feb. 25, 1947 FOREIGN PATENTS Number Country Date 19,170 Great Britain 1906 117,761 Great Britain Aug. 1, 1918 354,886 Great Britain Aug. 20, 1931 OTHER REFERENCES Conversion of Petroleum, by Sachanen, pages 374 and 375. Published in 1940 by Reinhold seconds at 100 Fahrenheit and having a refrac- 7 5 Publishing Company, New York.

Certificate of Correction Patent No. 2,485,103 October 18, 1949 GERARD S. MAPES ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 3, line 55, for the numeral 162. read 1.62;

and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office. Signed and sealed this 28th day of March, A. D. 1950.

THOMAS F. MURPHY,

Assistant Oom'mz'ssz'oner of Patents. 

